Britain has sent in Royal Navy ships to protect trawlers in the disputed Icelandic 50-mile zone as the so-called "cod war" escalates.

Three frigates - the Cleopatra, the Plymouth and the Lincoln - are sailing alongside the British trawlers now fishing in box formation.

The skippers had said they would not return to the seas without naval protection against Icelandic gunboats. They have been cruising the area since Iceland extended its fishing from three to 50 miles eight months ago.

The Navy is not going to stand idly by and see trawlers chivvied as they have been chivvied recently. The Navy has a job to do.

Joseph Godber, Minister for Agriculture and Fisheries

He said the frigates, armed with light guns and rocket missiles, would take "appropriate action" if necessary.

The decision to send in the Navy was made three days ago by the Cabinet Defence and Overseas Policy Committee with the Prime Minister Edward Heath present.

The trawler owners and the skippers had disagreed over whether or not to accept naval assistance.

The trawler owners feared that the Royal Navy's presence would restrict fishing as happened some 13 years ago during the first cod war.

But they have since agreed to let the frigates accompany the fishing boats because three tugs - the Statesman, the Irishman and the Lloydsman - would also be present and allow the trawlers to fish more freely.

The Icelandic ambassador in London, Niel Siguurdsson, said last night he was "surprised and disappointed" by the move.

Last week, the British ambassador, Sir Ian MacKenzie, failed to get assurances from Iceland's prime minister, Olafur Johannesson, that its ships would stop threatening British trawlers.